Range-finder or telemeter.



A. BARR & W. STROUD. RANGE FINDER 0R; TELEMBTER.

APPLICATION FILED DEU.2.1903.

Patented Dec. 28, 1909.

4 SHEBTSSHEET l.

A. BARR & W. STROUD.

E FINDER OR TELEMETER. APPLlUATION FILED 11m 1903.

RANG

Patented Dec. 28, 1909.

4 SHBETSSHEET 2.

A. BARR & W. STROUD. RANGE FINDER 0E TELEMBTER.

APPLIOATION FILED DEC2,1903.

Patented Dec. 28, 1909.

4 SHEETS-SHEET 3.

mw wk 2 A. BARR & W. STROUD'. RANGE FINDER 0R TELEMETER.

APPLICATION FILED DEO.2.1903.

Patented Dec. 28, 1909.

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UNITED sTATEs LBCBIBALD BAH-I. O! GLASGOW,

soomnn, aim 'wuuut s'raoun. or means.

ENGLAND.

RANGE-FINDER 0R TELEIIE'PEB.

Specification of Letters Patent.

Patented Dec. 26, 1909.

Application filed December 2, 1903. Berlal Io. 183,506.

To all whom it man comm:

Be it known that we, Ancumam BARR, of Glas on. Scotland, and WILLIAM Sworn), of Lee s, En land, have invented certain new and use 01 Improvements in Range Finders or Telemeters, of which the following is a specification.

Our invention has reference to improved rangcfinders of the single observer, short base type.

The new or improved arrangements to be described are applicable not only to ranfiefinders working on the coincidence princip c, but also to rangetindezs working on the stereoscopic principles.

Figure 1 1s a sectional plan and Fig. I a sectional elevation of a rangefincler workon the coincidence principle and cmtlicldying ourzpresent improvements. Fig.1}? sumo through the and 2" nre'correis a cross section. of the y ce B g .1 spending views of an instrument of a modified construction Figs. 3, 3' and? are corresponding views of arangefinder embodying our present improvements but constructed to work upon the stereoscopic principle. Figs. 4 and 4' represent a type of end reflectors suitable for use in the instruments shown in Figs. 1 and 3. Fi s. 5 and 5' show a type of end reflectors which we call inverting optical squares suitable for use in the instrument shown in Fig. 2. Figs. 6, 6, 7,7" and 7", and 8, 8 and 8 re resent three types of central reflectors or eyepiece prisms suitable for use in the instrument shown in Fig. 1. Figs. 9 and 9 represent a type of central reflectors (or eyepiece risms) suitable for use in the rangefinder illustrated in Fig. 2.

In the various figures D and D" roprcsent compound reflectors constituting o tical squares which are mounted at the on s to the outer casing E. These reflectors rcceivc the beams from the distant object and after double reflection dircct them toward the center of the casing.

G is an inner fmmo, shorter than the casing which may conveniently be of tobulur form and which is carried within E in such a manner that forces applied to F. in the working of the instrument will not sensibly deform the inner fmuue .6. Such a system of support is shown in the li urea as constituted of a gimbal K townr the left hand and 'of the inner framo (l, and u bearing L toward the right hand end of G, consisting of a partial sphere R attached to G resting in a ring S attached to E.

F and F are objectit'es located within the outer casing between the end reflectors and center of the casing through which the beams directed by the end reflectors ass. In the form of construction illustrated t ese objectives are carried at the ends of the mncr frame.

H represents reflectors located centrally in the casing which direct the booms outward to the eyepiece. In the case of instruments working on the coincidence rinctple the right eye only is IlSLd in indlcin an observation. and in that case it is pre arable to combine with the eyepiece prisms a seporating prism operating in the manner descmbed in a former patent No. 583,243, 02.1897. In the accompanyi drawings the-separattnfifigge is shown at' in l" and 2, and in the detail drawings of eyepiece prisms 7, 8 and 8", 9 and 9.

B represents the right eyepiece which in the case of rangefinders working on the coincidence principle as shown in Figs. 1 and 2 is alone used in making the observation. In these figures J represents a left eyepiece that may be used in viewing an illuminated scale placed within the outer casing E. In the stereoscopic rangefinder embodying our present improvements, both eyes are necessully used in making observations, and .in that case two eyepieces B and B, Fig. 3, are used, each having in front of it an eyepiece prism s stem as shown at H and H m Figs. 3 an 3.

M and M represent two positions of o refracting prism adapted to be moved along the path of one of the beams after it has traversed the objective, viz., in the examples of construction illustrated, the one from the right hand end of the instrument. This feature and the general mode of operation are common to rangefinders of the type to which this invention relates. In the operation of instruments wot-kin on the coincidence principle shown in lugs. 1 and l, 2 and 2, two separated images of the distant object are formed and by adjusting the re fracting prism M these are brought into coincidence orplincmcnt, the dept-cc of ad justmeut required being rcco ed on the scale thereby indicating tho range of tho obj cct observed.

The mode of operating the stereoscopic rangefinder shown in Figs. 3 and 3' is sumlar to that of the well-known Grousellier (or Zeiss) stereoscopic rangefinder except that in the present instrument there are two fixed marks, one in each field in the focus of the eyepiece, (say) upon the faces Nf and N (F 1g. 3) and N (Fig. 3") of thefiprlsms, and the refracting prism M is mov to the direction of the le h of the tube by any suitable mechanism so as to alter the 051- tion of the image of the distant 0 ject formed by light entering at the right hand end of the instrument and passin through the ob'ect lass F relative y to t e image forme by ight entering at the left hand end so as to make the image appeszr to be at the same distance from the o rver as the ima e of the two fixed marks, when a scale suitably graduated and worked in accordance with the motion of the refracting prism M will indicate the distance of the objlect observed.

he new feature of the present invention consists in a new combination of optical and mechanical parts. In our former patents, in which two objectives are used, one at each end of the instrument (Nos. 567675 of 1898, 583243 of 1897) single reflectors were used at the ends of the instrument. An bending of the frame carrying these refliictors would consequently affect the indications of the instrument, and this necesitated the ca g of the reflectors on the inner frame 0 the instrument. In the new form of rangefinder hereindescribed we use at the ends of the base a compound reflector constituting an o tical square, and as the angle set out by sue a square is practically independent of movement of the square about an axis parallel to its reflected surfaces, the sqi are can be attached to the outer casing. his leads to a lighter and more convenient construction than that of our former instruments. These features we use in conjunction with others forming a new combination of parts constituting an improvement of hitherto known practice. We show two systems of producing erect images in instruments of this type. In Figs. 1 and 1 the end reflectors are of non inverting type of optical square, and in order to show erect images we reflect each beam, in a vertical plane in the central reflectin combination. Figs. 6 and 6 show a simp e method of erecting the images. In this case the beams of light, after reflection in a horizontal plane from surfaces 0 and O res ctivcly, are reflected in a vertical lane rom a surface A. The observer looks Irectly downward in viewing the images, and further, with the simple arran ment shown, the Images are not separnt by a se crating line.

igs. T, 7 and 7" show a preferable construction. The beams are refracted on entrance to the prisms at the inclined face P and I (the prisms are shown constructed in the well-known manner, of the two kinds of glass, so as to produce approximate achromatism) and strike the vertical refleeting faces 0 and O with a downward and upward inclination respectively. They next strike an inclined surface A, by means of which they are reflected in a vertical plane so as to fall at the separatin edge C, and after refraction thence (as escribed in our earlier patent No. 583243 of 189?) they pass through an eyepiece directed downward at 45 (or other convenient angle This constitutes a new and important improvement in rangefinders, for not. only do we secure erect images when usin non-inverting o tical squares at the end: of the case, an the advantage of having the images separated at a separating line but also a downward inclination of the eyepiece which admits of the observer takin a much more comfortable attitude, eit er when holding the instrument in his hands (standing or sitting) or when kneeling or lying prone with the rangefinder rested upon a low support. It also allows of the instrument being placed much nearer the ground than is possible with the instrument in which the observer looks in the plane of triangulation, and this greatly facilitates the taking of cover from the enemys observation when the rangefinder is used in field operations.

We are aware of the earlier patent granted to Brown and others, No. 738155 of 1903, in

which the use a reflector to direct the beams of li ht ugh an eye iecc directed downwe at right angles to &e plane of triangulation and we do not claim the arrangement therein described, which does not accomplish the end we have 1n view. In Browns patent the reflector is at the end of the base, and thus leads to a type of instrument that cannot be held and used in the manner we provide for in the present application where the eyepieces (or eye iece) are situated at the center of the lcngt of the instrument. so that the rangefinder can be conveniently held in the hand, or conveniently handled when mounted on a stand. Further, in Browns rangefinder a single objective is used and the advanta es of a sepnrating lit however, it may be preferred to so mnstruct the rangefindcr that the observer looks horizontally toward the distant object while using the instrument. eyepiece prisms of the form shown in llgs.

8, 8' and 8" may be used. These prisms tother with non-inverting optical squares at t e ends of the instrument give erect Images and also provide the separating edge C. I t will be observed that in this case the distinction is that the beams are reflected m a vertical )lane from two reflecting surfaces A and before they are reflected in the horizontal plane from the surfaces Q and instead of from one surface (Fig. 7) after reflection on the horizontal plane.

When inverting optical squares are used at the ends of the instrument, as in Figs. 2 and 2, it is not necessary to a in reflect the beams in a vertical plane. n this case eyepiece prisms such as those shown in Figs. 9 and 9' may be used, having a separating prism as shown at C.

Claims.

1. The combination in a rangefinder of the short base single observer type, of an outer casing, a compound reflector at each end of the outer casing, a shorter inner frame within the outer casing, a gimbal supporting the inner frame at one side of the center, a s herical bearing supporting the frame at the other side within the casing, an object glass at each end of the inner frame, and a set of reflecting prisms at the center of the inner frame, substantially as set forth.

2. The combination in a rangefinder of the short base single observer type. of an outer casing carrving at each end an optical square. a mortar inner frame sup rted within the outer casing, an object ass at each end of the inner frame a set 0 prisms at the center of the length of the inner frame oomprisin reflecting surfaces approxinmtcly at right angles to the plane of triangulation and inclined at approximately to the base line of the instrument for reflecting the beams of light in a direction approximately at right angles to the base line. and u separating edge at which the images :mfocused formed upon one part of the central reflecting combination. substantially as set forth.

:3. The combination in a rungefindcr of the short lmsc single-obsrrwr type, of an outer casing carrying at cut-h cud an optical square. a shorter inner frame supported in the outer casing. an object glass at curb end of the inner frame. a set f prisms at the center of the length of the inner frnmc comprising reflecting surfaces approximately at right angles to the plum oi? triangulation uud lllt'llttt'tl at approximately to lhc base line of tlu Instrument reflecting the bvums of light in n direction approximately at right angles to the base line, and u sepa- In some such cases.

rate prism through which the beams of light pass on their way to the eye of the observer. said prism having a separating ed e at which the images are focused, all so 15h"!- tiully as set forth.

4. The combination in a rangefindcr of the short base single observer type, of an onto casing carrying at each end a non-inverting optical squat-0,11 shorter mner frame supporter in the outer casing, an object glass at each end of the inner frame, a set of prisms at the center of the lepgth of the inner frame comprising reflecting surfaces approximately at ri ht angles to the plane of triangulation and inclined at approximately 45 to the base line of the instrument for reflecting the rays at approximately right angles to the base line, a reflecting surface at an angle to the plane of trian u lation adapted to erect the images, an a separating edge at which the ima es are focused formed upon one part of t e central reflecting combination. substantially as set forth.

5. The combination in a rungefinder of the short base single-observer type, of an outer casing carrying at each end a non-inverting o tical square, a shorter inner frame snpporte in the outer casing, an object glass at each end of the inner frame, a set of prisms at the center of the length of the inner frame comprisin reflecting surfaces at right angles to the plane of tria ulation and inclined approximately 45 to t e base line of the instrument for reflecting the rays at approximately ri ht angles to the base line, a reflecting sur ace at an angle to the plane of triangulation adapted to erect the mm es, and a separate prism through which t 1e beams of light pass on their way to the eye of the observer said prism having a separating edge at which the images are focused substantially as set forth.

6. The combination in a rangefindcr of the short base single-observer type, of an outer casing carrying at each on a non-inverting optical square, a shorter inner frame supporter in the outer casing, an object glass at each end of the inner frame, a set of prisms at the center of the length of the inner frame comprisin reflecting surfaces at right angles to the p one of triangulation and inclined at approximately 45 to the base line of the instrument for reflecting tho rays at approximately right angles to the base line, and two reflecting surfaces atwhich the beams are respectively reflected, in a vertical plane to cause the images in appear erect. substantially as set forth.

I. 'lhe combination in n rnngofindcr, of an outer casing carrying at each end an optical squnre, a shorter inner frame supported in the outer casing, an ob'ccl glass at; cnch end of the inner frame, um sets of reflecting prisms nonr the center of the length of the lit) inner frame for reflecting the beams of ll ht in a direction approximately at right ang es to the base line, substantiallz as set forth.

8. A rangefinder of the a ort base singleobserver type having reflectors at each end of the base arranged to direct the beams inward toward the center of the base, two ob jectives arranged between the end reflectors and the center of the base through which the beams of light respectively pass, a central reflecting pnsm combination adapted to diroot the beams of light upward at an angle to the plnne of triangulation and a downwardly dlrected eye-piece, substantially as set forth.

In testimony whereof we aifix our signaturns m presence of two witnesses.

ARCHIBALD BARR. WILLIAM STROUD. \Vitnesses:

JOHN Lmnnn, JOSEPH HENRY Pmneon. 

